How to add Window 7 version

I might not be in the right place and if im not i apologize. My question is this.. I have a Dell Windows 7 Ultimate x64 DVD. I have a Home premium DVD also. Ive been trying to make one disc but it will only let me install ultimate. I have modified the ei.cfg (added HomePremium and Ultimate) i have exported the images via imagex (from WAIK) (imagex/export <folder of extracted image>/sources/install.wim 2 (which is the home premium image) <output install.wim>which all worked, but when i boot off the flash drive im back to ultimate only. What am i doing wrong? when i check the slp.cmd it has the ultimate serial to insert do i need to change it to the home premium? Thanks for any responses